mailboxes disappeared in Mojave
I've just - with the help of the Genius Bar - installed Mojave. It's sketchy, and I have a few issues I shall post separately.
This one is this: I have Mail up and running. My "On My Mac" mailboxes have disappeared. I've clicked "Show" and what I get is one folder with one message. In my system folder, under Mail/V5/0A78DEB9-9B8B-46CB-9305-8B95D7C4EECA I see them all.
I looked at Import Mailboxes, but I can't, in the dialogue, get access to my User System Folder (can't see it)
iMac 27", macOS 10.14